As previously stated, I would first ohm out the compressor and test the capacitor. Then I would cap off the liquid line and suction line connections, there is no need to loop them. I would then hook up my gauges, attach to jug of R-22, purge the air, and pressurize hoses to 5 psig. Then I would open the service valves to see if the system is even pressurized with refrigerant. If not, game over, you have a leak somewhere. (I guess at that point you could pressurize the system with nitrogen to see if you can identify the location of the leak.) If there is still refrigerant in the system, I would then slightly pressurize the suction side with vapor only, say 50 psig. Then manually depress the contactor and see if the compressor will even turn over. If it does work it will give you a chance to verify the pumping capacity of the compressor. It would be no different than pumping down a system. Your high side would be tied off and the compressor would only be pulling from the low side.